Rotary drill bit apparatus



March 13, 1951 w, KAMMERER 2,545,037

ROTARY DRILL BIT APPARATUS Filed April 8, 1949 2 Sheets-Sheet l 11v: 'ENTOR.

1420/52 WKAMMERER, 6! 31 BY HTTOQNEY- A. W. KAMMERER ROTARY DRILL BIT APPARATUS March 13, 1951 2 Sheets-Sheet 2 Filed April 8, 1949 INVENTOR. Alec/v52 W JZWIIMEREE,

IQTTOQNE'Y.

Patented Mar. 13, 1951 omits-n earner --O F F-I"C E I -2, s45,03v

ROTARY Ditin BIr-APPARATIis "Archer W. kammereriruueiwn, est-iii. Application -April 8, 1949, =Serial* No. 86,161 ivoiaims. (c1.-*-25s=76) The present inventionpertains todrili'bits; and is more particularly directed to-'rotaiy'bits embodying expan dible cutters for drillingiiolesbelow casing, or other well eonduits, that are greater in diameter thanf-thej inside diameter of the -casingstring through when "the "bits are capable of passin'g.

Thisapplication is a continuatien in -part of 'my apli'cationsior -R6taify DrillBits, Serial No. 597,744., filedJune'fa ie is, 'riew patent N0. 2,466,991,"Eiipansible Rotaiy-DrilllBits, Serial No. ea'egsoe fil'ed Jul 29, 129516; and gpan me Drill Bit, serial: 4Z3,789,{fiIed Augustijz, 194.8.

In'eX'panSibIe drill'bitsofithe type described in my above identified"appliatioiis, the expandible cutters can be held normally retracted position by a latch device. Theciittrs'hiayfbefheld that "condition 'to perinit lowering or the drill bit through anbpen well bore to tlie "depth at which the holefenlarging op'eration'is to 'commence. Whe'nthis point is reached, the latch device is removed, to aliow jthe cutters "to be expanded outwardly to' a'posi'ti'dn enabling their production of an enlarged diaineterhole.

Following their outward expansion 'ito their fullest'extent, the cutters are locked n that position by "a "telescopic devie 'inoirable behind the cutter supports. Ffluidcanhe purriped down the drill string and telescopic device"f'or aetion uponfthe expandjible cutters, "to "maintain them free from "formaue Cuttings and insure their proper penetration ihtdtheforniation. A

Anobject eflthe' present invention is t'o provide a rotary 'drill bit of the; character "above in'dh cated, embodying 'a modified device forjr'etain ing the expandible cutters initially inre'tracted position, "and "for releasing such cutters "when 'their outward expansion is desired Still another object of the inventionis to provide a latch arrangement for holdingftl'i'e" e'iitters initially ini'retraote d position, and which butters are released, when desired, by positivelyagt'in mechanical instrumentalities forming part of "the drill 'bitit'seli,

A further object of theinvention istoprovidefa rotaryfexpansible'drill bit, in "which the latch device for holding the "cutters initially retracted is released 'by atele'scopic"mandrel, or similar device, which serves to 'holdth'e cutters 'in their outwardly expanded position.

Rotary expansible drill bits are sometimes employed in connection with a 'nen- 'expansible bit, which is adapted 'toa'ct'i'ipon the bottom of the hole and forinthe central portio of 'the hole.

In general, the ma or-portion of theidrination mater al jis "renewe b this diill'hit, "the expan'sible drill bit emergin the well "bore thus produced.

mean condition.

Yetanotherpbject of-the invention is to procutters are locked "outwardly in their laterally feirpa'nded position by a elescopic inandrel' which isc'apable of insu'ring'a supply of a large volume of drillingfluid'to' a' non' 'expandible drill bit-positioned below the 'eiipandible drill bit.

This inventionpossesses rnany other advantages, andfhas other objeets which-may be made more clearly apparentirom a consideration of a form iiihich it maybeernbodied. This form is shown in the drawings accompanying and formingpart of the present specification. It will now be described in detail, for the purop'se of illustrating the general principles-oi the invention; butit is -'to be understood that suchdetailed description is not to betaken in=a limiting sense,

since the scopeofthe invention is'best defined b'y-the appended claims.

Referring to the drawings:

Figure l is a side -elev-ation, ena reduced scale, showing a'drill bit-apparatusembodying the invention;

a longitudinal section-taken along the iine -2-2 en 4 Fig. 3, of the drill *-bit apparatus disposed within-a well bore, withtheparts of the expandible bit portion occupying their initial retracted position;

Fig. '3 is-a cross-sectiontaken along the line 3+3 on Fig. 2'; e

*Fig. 4 {is an --eniarged view similar --to Fig. -2' of the apparatuswiththa 'expandible cutters locked in their outwardly expanded positions;

=Figsx5; 6-and =7 are "cross-sections taken along the lines *5-"-5, -=6-=6 "and i=4, respectively, of Fig.4.

shown in "the drawings, the rotary drill bit apparatus A"'is"'attached"to a' s'tringef drill pipe B, by means of which it is'-l'6weredthrough a well easing C in'awellbdre D"tbfa poirit below a casshloe "E, 'at'whie'h the hole isto be deepened 'andeiilargd to a'diahiter greater 1 than the in.-

3 side diameter of the well casing through which the apparatus must pass.

The apparatus includes a non-expansible pilot bit G at its lower end for drilling the central portion of the new hole. It also includes an expansible drill bit portion H for enlarging the bore hole produced by the pilot bit, by forming and operating upon a formation shoulder J, as hereinafter described.

The upper end of the expandible bit H consists of a driving mandrel II, whose upper pin I2 is threadedly connected to a sub I3 forming the lower end of the drill pipe string B. This mandrel includes an upper kelly or drill stem member I4 slidably splined to the main body I5 of the bit. As disclosed in the drawings, the exterior I4a of the kelly is hexagonal in shape, and is telescopically received in a companion hexagonal socket I50. within the body. The mandrel II has a limited range of longitudinal movement within the body, its upward movement being limited by engagement of an external shoulder I5 on the kelly with a retainer ring I? at the upper end of the body, suitably secured thereto, as by the use of welding material I8.

The body I5 has a plurality of expansible parts mounted on it, comprising cutter supporting members I9 pivotally mounted in body slots 29 on pivot or hinge pins 2I suitably secured to the body, as by the use of welding material 22. Each cutter supporting member consists of a depending leg 23, having a bearing supporting pin 24 inclined inwardly and downwardly, and

on which a roller side cutter 25 is rotatablymounted. Anti-friction roller and ball bearing elements 25, 21 are preferably placed between each cutter 25 and bearing pin 24, the roller bearing 26 transmitting radial thrusts and the ball bearings 21 both radial and axial thrusts. The ball bearings '21 also retain each cutter on a pin, being inserted in place through a passage 28 in the bearing supports, which is then closed by a plug 28 welded to the pin 24. The plug or pin 29 depends from the passage 28, and is used to hold the cutters 25 in retracted position, as

pointed out below.

Each cutter supporting member I9 also includes an upwardly extending arm 30, against which an elastic expander 3I bears. This expander, in the form of a compressed coil spring,

is received within a retainer pocket 32 in the.

body I5, and exerts its force against the arm 30, tending to swing it inwardly and thus urge the cutter 25, on the other side of the fulcrum pin 2I, in an outward direction. The extent of this outward movement is limited by engagement of stop shoulders 33, 33 on opposite sides of the cutter supporting member I9 with cooperable body stop shoulders 34, 34.

After the cutters 25 have been expanded outwardly by the expander springs 3I to the maximum extent, they can be locked in this position by a tubular member 35 of the mandrel I I which is piloted in the kelly I4. This member is provided with a lock' portion 41, movable from an upper position in transverse alignment with infor longitudinal movement in both directions. This is accomplished by providing an anti-friction thrust bearing between a boss or shoulder 39 on the tubular member and the kelly I4. The shoulder 39 is received within a lower socket Mb in the kelly and has a toroidal raceway 10 on its exterior, around which a plurality of bearing balls 'II can ride. These balls are also received in an opposed toroidal raceway '12 in the kelly.

The balls II are insertable into the raoeways through a hole or passage I3 extending through the external shoulder It on the kelly and communicating with its internal race "12. After the balls have thus been disposed in position, the hole is closed by a suitable pin or plug M, which is prevented from moving outwardly of the kelly by the inner wall of the surrounding body !5.

The tubular member 35 has an upper portion 35a extending into the central bore Md of the kelly, with the upper terminus 15 of the member 35a flaring upwardly and outwardly, to enable fluid pumped down the drill string B to flow smoothly into the central passage 35c through the tubular member 35. This fluid is prevented from flowing around the exterior of the tubular member 35 by suitable packing 11 disposed between the upper portion 35a of the tubular member and the kelly adjacent the upper end of the tubular member shoulder 39'.

The arrangement between the tubular member 35 and kelly i4 is such that both downward and upward movement is transmitted between the kelly I 4 and tubular member 35 from one raceway 1a or 12, through the ball bearing elements 1| to the other raceway 12 or 10. In this manner, the kelly l4 and tubular member 35 are caused to move jointly in both longitudinal directions, but they are free to partake freely of relative movement therebetween.

The mandrel II is normally held in its upper position with respect to the main body I5 of the bit and the supporting members I9 by a helical retractor spring 38 encircling the tubular member 35, with its upper end engaging the mandrel shoulder 39 and its lower end engaging a spring seat 45 at the lower end of the hexagonal body socket I5a. This spring seat 40 also serves as an upper bearing guide for the tubular mandrel member 35, whose lower end is slidable within a lower bearing guide 4! below the lugs 31, which bearing guide is integral with the main body I5 of the expansible bit and interconnects the depending webs I5c of the main body together. The two guides 40, il form a spaced two-point support for the mandrel member 35, and assist it in resisting inward movement of the cutter legs 23 to retracted position during the reaming or cutting operation;

The lower member 4| not only serves as a bearing guide for the tubular mandrel member 35, but it is also formed as a threaded box for receiving the upper threaded pin of the lower non-expansible drill bit G. This drill bit may be of any desired form, being shown, for reasons of simplification, as 'a drag bit having cutter blades 3! capable of operating upon the bottom K of the bore hole. These cutter blades 8| have passages 82 extending from a central passage 83 in the pin portion 80 of the lower drill bit to the forward faces of each blade.

The tubular mandrel 35 extends downwardly below its guide 4|, and preferably slidably into the central passage 83 in the lower drill bit G. Leakage around" the exterior of the mandrel 35 maybe prevented by providing "a suitable side armamenseal fil in'ar -peripheral: groover-85i'on the.mandreli 3 adapted to' slidably -and: sealinglyrfitthe wall the centra-Ppassage:

Girculating fluid can pass downwardlyathrough; thestrin'g of-drill pipe-B and through the-tubular n'i'andrel" H intothe -central passage 83-" of-- the lower-drill bit GE Erom this point; the dr-illing fluid flowsthrough -the-nozz1es--'or-- passages 82 tothe-forward facesof thebii?cutters-84; discharg-- ing' from these cutters to-cleanse them-"of" cuttings and-fiuslr-the latter f-iom'the drilling area to the top of the well borel Duringitsup' ward passage; the circulating 'fl'uidpassesaround the expansible cutters and also maintains them cleanof'cuttings:

The cutters 2 5- may be retained initially in re'- tracted: position against the expa-nsibl'eforcesof the springs 3| by means of a meclrianically-'re leased trip-device.- This device" includes a hold- .ing-plateormember 86* disposed around thelower portionof the tubular member 3'5 immediately below" an external flange 81* formedinteg-rally with, or'otherwise suitably securedto, thetubular member; Theholdingmember has spaced holes 88in its outer portionfor receiving the'lowerends- Z-Ea of" theballbearing plug orrpins 29:

When the holding deviceBfiis disposed over the pinsZB; the cutter supporting members H) are prevented from expanding under the influenceof the springs 31, thereby holding the cutters 25 in retractedposition; I-tisto benoted thatthepins 29* are inclined initially ina" downward and slightly outward direction,.. so' as toprevent the holding member from moving downwardlyuntil purposely released, which? downward" movement would allow outward expansion of'tne' cutters25": Suclr releaseoccurs as a result" of downward movement of the tubular member which-Will move-its external flangeill-against the holdingmemberflfi and shift it dbwnwardly ofithepins- 2'9; During lowering of the'a-pparatus to'the-bottom of the hole, the holding device BQre-tains the: cutters25- inretracted position; The-efiectivediameter of the lowerorpilot bit is less than the inside diameter" of 5 the well casing G through which the drill bitapp aratus is to pass,- and this is also true" of the retracted efieetived'iamet'er ofthe expandible cutters 25; Whenthe bott'om' K of the well borehas been reached, the pumps atthe top of the hole are started and drilling fluid pumped down thedrillstring-B. This drilling fluid passes through the tubular memberlifi and through the pilot bit passage 83*andnozzles 82 to the bottom of the hole.- Rotation of the drillstring and the apparatus may then commence, to cause-the pilojt" bit G'to'drillahead in the well bore. At the commencement of such rotation, the drill string B; mandrel H and its tubular member 35 maybe moved downwardlyto a slight extent to cause the externalmandrel flange 3 1' to-engage the holding member 86-and to shift it downwardly suflibiently to remove-it= from the pins 29,- freeing the cutters 2'5 and theirsupportingmembers I9 and allowing the springs 3 i to expand; These springs will shiftthe arms 38 inwardlyand the cutters 25 outwardly against the formation. v

Rotation, of the drilla string B is continued, to rotate the expandiblebi-t body-- [5 through the splined kelly and body corrections: we and 15a, until the sidecutters- Z5 enlarge the-diameter of the hole produced by the pilot bit' to the maximum extent, asdetermined by eventual abutment of-the supporting member stop shoulder 33 with the companion body-"'stopshoulder-34; When thisnfull diameter hasibeen: aohifive a ie formal-i tiomshe'ulder J :has; beeneprodil ed n the well;

bore; by; the; cutters 525; ;-under the action ,of; the

expander springsfiil: Ail-this timmdril-lingweight;

may be: imposedrupon'rthetdrillingwstring B3; shifte engages-the upper spring; seattand guide 1, 1.

downward movement also; shifts: the: t1.1b.\1. fl v member; 3:512 downwardly;. because" of: the interlocking;- balli thrust: bearing 10; 1 l-, '|'2;, to position the: mandrel; or: tubular, memberlocl; portions 4 1 opposite and in: alignment Withi the lugs-31 on the inner2portionsaoflthe;cutter; supp rtin m me bers l9, providing a positivezloclo and-preventing inward movement of thei,cutters=-25 il ig; 4),

It is to. be noted that afterithep ot-bi.t, G-= haS; reached r thebottom 'Kg'of j theahole; the=d-rill string B iszlowered toonly-a slight-extent;rwhich;is=suf fici'ent to engage: the mandrel flange or shoulder, 87' with the latch plate;85;. and release-itiromthepins-ZQ. The lock portion His-disclosed inia tially above the lugs 31 onthecutter supporting:

: members 19*, toallow the latch device- 86' tobe released without thel'ugs 31-1 offering, any interferenoe to lowering ofrthe: tubular "mandrel 35;. However, aftersuch release; andilfollowing the production of the formation shoulder: J; as. ex-

; emplified'in Fig. 4,, theinecessary drilling weight site and within the lugs;

During .the. downwardrtelescoping ofrthe E'bllbll'r larqmember 3.5twit-hin the. main vbit: body l'5;, its; lower;-portioIr-will alsoislide; downwardly; within: the: central: passage 83:: inathe lower drill bit; Fluid may: be: circulated; throu h the; dril1- bit,. tubular; mandrelz and? the pilot: bit-r passages.- to insure propens flushing; rofg; the cuttings from the bottom ofothez'hole=anck'alsofroimthe areaoftheformation-shoulder l'toi the top of; -the well;bore=- Drilling-is cor-itinued by; rotating: the drill-bits and. imposing the proper drillin weight anther various out-terstl 25;, to cause their removal; ofthe formation material at the bottom of. the; hole; and-f enlarging: or; the; pilot hole. in adoyvnvvardz; direction top the desired extent: or length; W-hemthe1drillrbitzis to be retracted and removed; to. therto-py of thewelk-bore; thedrill string; B islelevated; moves the: side: outters. 2fi-alb0veithe formation? shoulder J and v11ermits the retractor spring 38 to; press; relatively downward: on-the body l-5an'd ,move it; together with the cutter supporting members: l9; downwardly with respect to themandrellfl Thisactijomrepositions-themandrel-lock portion, 4'1ioppo.-; Sitethe:sunportinglmember recesses-316," and abovetheir lugs 31, becauseof; the; ballrbearing c011,:- lingrj l l, yermitting inwardeswingingaof-ythe =cuttors: 25: and their supporting: member-s5 I19: when: the toolipasses back intorthe; casingzQuponzelevationzof; thedrillstringB. The; cutters HZSLand; their supporting;- members: l9 .1 will" ride the; wall of; the; casing; during elevation of; the string: B; untik theitool' isz removedcfronnthetop-ofithewell bore. During this: elevation, thelatch plate 86" merely rests upon the upper end: of the-box portion 4| of the'pilot.bitfbodypwithout interfering with-the" operation of the equipment.

' It'is, accordingly, apparent-that arotary drill bit: apparatus hasbeen provided; that; iscapabl of-produeinga pilot=hole, -as well= asw enlarging the 7 hole to the' desired diameter, which is greater than the inside diameter of the well casing C through which the apparatus is capable of passing. The expandible cutters 25 are held initially by positive means in retracted position, and are removed mechanically by positive means when the bottom of the well bore is reached. Release of the cutter latch 86 is effected by the tubular member 35, which serves to lock the cutters 25 outwardly in their fully expanded position. This locking member also insures the delivery of an adequate volume of drilling fluid to the pilot bit G, and also insures the removal of the cuttings from the bottom K of the well bore, as well as from the region of the formation shoulder J The inventor claims:

1. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a mandrel slidably splined to said body and adapted for connection to a tubular drill string; means'engaging said cutter means for expanding said cutter means laterally outward independently of movement of said mandrel along said body; releasable latch means connected to said cutter means for releasably holding said cutter means in an inward position against the action of said expanding means; and means on said mandrel movable therewith, and engageable with said latch means to release said latch means from holding said cutter means in an inward position upon movement of said mandrel relative to said body.

2. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body"; a mandrel slidably splined to said body and adapted for connection to a tubular drill string; means engaging said cutter means for expanding said cutter means laterally outward independently of movement of said mandrel along said body; releasable latch means connected to said cutter means, for releasably holding said cutter means in an inward position against the action of said expanding means; means on said mandrel movable with said mandrel in one longitudinal direction along said body, after expansion of said cutter means, into engagement with saidcutter means for preventing inward movement of said cutter means; and means on said mandrel movable therewith, and engageable with said latch means to release said latch means from holding said cutter means in an inward position upon movement of said mandrel in said one longitudinal direction. I 3. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a mandrel slidably splined to said body and adapted for connection to a tubular drill string; means engaging said cutter means for expanding said cutter means laterally outward independently of movement of said mandrel along said body; latch means disposed around said mandrel and releasably connected to said cutter means for releasably holding said cutter means in an inward position against the action of said expanding means; and means on said mandrel engageable with said latch means for releasing said latch means from said cutter means upon movement of said mandrel relative to said body.

4. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a mandrel slidably splined to said body and adapted for connection to a tubular drill string; means engaging said cutter means for expanding said cutter means laterally outward independently of movement of said mandrel along said body; latch means disposed around said mandrel and releasably connected to said cutter means for releasably holding said cutter means in an inward position against the action of said expanding means; means on said mandrel movable with said mandrel in one longitudinal direction along said body, after expansion of said cutter means, into engagement with said cutter means for preventing inward movement of said cutter means; and means on said mandrel engageable with said latch means for releasing said latch means from said cutter means upon movement of said mandrel in said one longitudinal direction.

5. A rotary well drilling bit adapted to be connected to a tubular drill string: including a main body; cutter means carried by said body and movable laterally of said body; means en-- gaging said cutter means for expanding said cutter means laterally outward; releasable latch means connected to said cutter means for releasably holding said cutter means in an inward position against the action of said expanding means; and means connectible to the drill string and slidable within said body into engagement with said latch means, in response to longitudinal movement of the drill string, for releasing said latch means from holding said cutter means in an inward position.

6. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; means engageable with said cutter means for expanding said cutter means laterally outward and for preventing inward movement of said cutter means from such outward position, said engageable means comprising a mandrel slidably splined to said body and adapted for connection to a tubular drill string; releasable latch means connected to said cutter means for releasably holding said cutter means in an inward position; and means on said mandrel movable therewith, and engageable with said latch means to release said latch means from holding said cutter means in an inward position upon longitudinal movement of said mandrel relative to said body.

7. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; means engageable with said cutter means for ex panding said cutter means laterally outward and for preventing inward movement of said cutter means from such outward position, said engageable means comprising a'mandrel slidably splined to said body and adapted for connection to a tubular drill string; latch means disposed around said mandrel and releasably connected to said cutter means for releasably holding said cutter means in an inward position; said mandrel being engageable with said latch means for releasing said latch means from said cutter means upon longitudinal movement of said mandrel relative to said body.

8. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; means engageable with said cutter means for expanding said cutter means laterally outward and for preventing inward movement of said cutter means from such outward position, said engageable means comprising a mandrel slidably nlinedtosaidbody: and adapted fori onnection to-a -.-tubu lar. drill .rstring; for longitudinalmove: ment therebydnz one direction. to a-position hold: ing. said cutter means outwardly; releasable latch means :connected'to .-said cutter means .for releasably holding said cuttermeans. in@ :an in-:- wardposition; and meanson; said mandrel: move able therewith, and ngageable -with said. latch means to release said latch means from holding said:.cutter=t meansrinci-arrr inward position upon movement of said mandrel in said one longitudinal direction;

9. ,A rotary well drilling bit: including .a main body; cutter means mounted on saidbodyjor lat= eral movement with respect to said body; a drill bit secured tothe lower end ofsaid' main body, said drill bit having a fluid circulating passage; means: engageablefwith said ,-cutter means :for expanding -said cutter means .laterallyyoutward and for preventing inward movement of said out ter means from such outward position, said engageable means comprising a tubular mandrel extending into said passage and slidably splined to said body, means on said mandrel for connecting said mandrel to a tubular drill string.

10. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a drill bit secured to the lower end of said main body,

. said drill bit having a fluid circulating passage;

means engageable with said cutter means for expanding said cutter means laterally outward and for preventing inward movement of said cutter means from such outward position, said engageable means comprising a tubular mandrel extending into said passage and slidably splined to said body, means on said mandrel for connecting said mandrel to a tubular drill string; and means providing a slidable seal between said mandrel and passage.

11. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a drill bit secured to the lower end of said main body, said drill bit having a fluid circulating passage; means engageable with said cutter means for expanding said cutter means laterally outward and for preventing inward movement of said cutter means from such outward position, said engageable means comprising a tubular mandrel extending into said passage and slidably splined to said body, means on said mandrel for connecting said mandrel to a tubular string; releasable latch means disposed around said mandrel and connected to said cutter means for releasably holding said cutter means in an inward position; and an external flange on said mandrel engageable with said latch means for releasing said latch means from said cutter means.

12. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a drill bit secured to the lower end of said main body, said drill bit having a fluid circuating passage; a tubular mandrel extending into said passage and slidably splined to said body, said mandrel being adapted for connection to a tubular drill string; means engaging said cutter means for expanding said cutter means laterally outward independently of movement of said mandrel along said body; latch means disposed around said mandrel and releasably connected to said cutter means for holding said cutter means in an inward position against the action of said expanding means; means on said mandrel engageable with said latchc meansdor r,eleasing. .-said. latch means from saidcutter means upon movement of said mandrel in onelongitudinal. direction; ,and means on; said; mandrel movable with said .-man= drelim said one longitudinal direction .into v ens gagement; :with said ,cutter means: for preventing inward. movement ofsaid cutter-means;

13. rotary-well drilling bit including; amain body; cutter. means imountedon said. .body,,for lateral movement with respect to said..body.; .a drill. bitsecured toathe lower;- endof said 'main body, saiddrill bit havinga .iluid circulating .pass sage a. tubular mandrel extending .into,.saidpas! sage "andslidably splined. .tosaid body, saidma ldrel, being. adapted .for. connection to..a;.tubular drill-string; means engaging-saidcutter means for expanding said cutter..means...laterally..outa ward independently of movement. of; said, man; drel along said body; releasablelatch; means dis, posed around said mandrel and connected to said cutter means for releasably holding said cutter means in an inward position against the action of said expanding means; an external flange on said mandrel engageable with said latch means for releasing said latch means from said cutter means upon downward movement of said mandrel; and means on said mandrel movable downwardly with said mandrel into engagement with said cutter means for preventing inward move ment of said cutter means.

14. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a mandrel slidably splined to said body and adapted for connection to a tubular drill string; means engaging said cutter means for expanding said cutter means laterally outward independently of movement of said mandrel along said body; latch means disposed around said mandrel and releasably connected to said cutter means for holding said cutter means in an inward position against the action of said expanding means; first means on said mandrel movable with said mandrel in one longitudinal direction alongsaid body, after expansion of said cutter means, into engagement with said cutter means for preventing inward movement of said cutter means; and second means on said mandrel engageable with said latch means for releasing said latch means from said cutter means upon movement of said mandrel in said one longitudinal direction; said first means and second means being spaced on said mandrel with respect to each other so that said second means engages and releases said latch means upon movement of said mandrel in said one longitudinal direction prior to location of said first means in position to prevent inward movement of said cutter means.

15. A rotary well drilling bit: including a main body having a lower threaded member; cutter means mounted on said body for lateral movement with respect to said body; a drill bit threadedly connected to said lower member, said drill bit having a fluid circulating passage; means engageable with said cutter means for expanding connecting said mandrel to a tubular drill string.

16. A rotary well drilling bit: including a main body; cutter means mounted on said body for lateral movement with respect to said body; a

mandrel slidably splined to said body and adapted for connection to a tubular drill string; means engaging said cutter means for expanding said cutter means laterally outward; latch means con nected to said cutter means for releasably holding said cutter means in an inward position; and an operative connection between said latch means andsaid mandrel, whereby said latch means is released when said mandrel is moved relative to said body.

'17; A rotary well drilling bit: including a main body; cutter means carried by said body for lateral movement with respect to said body; means engaging said cutter means for expanding said cutter means laterally outward; latch means connected to said cutter means for releasably holding said cutter means in an inward position; instrumentalities movable with respect to said body and operatively connected to said latch means to release said latch means from said cutter means upon longitudinal movement of said instrumentalities relative to said body; and means on said instrumentalities for connecting said instrumentalities to a tubular drill string to enable said instrumentalities to be moved longitudinally of said body by the tubular drill string to effect such release of said latch means.

ARCHER W. KAMMERER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,243,998 Blau June 3, 1941 2,466,991 Kammerer Apr. 12, 1949 

